Pre-packaging operations of IC chips, which include operations such semiconductor substrate (wafer) mounting, wafer sawing, die separation, die transfer, and die attach are critical operations which demand care while handling wafers and their respective dice and die. Functional die damaged during these operations unnecessarily increase processing costs and reduce yield. One particular type of die substrate susceptible to problems during pre-packaging operations includes gallium arsenide (GaAs). Crystalline GaAs is brittle and predisposed to chipping and cracking.
In a typical pre-packaging operation, after wafers are sorted, they are mounted on adhesive tape. The adhesive tape provides support for the wafers during wafer saw, die transfer, and the die attach operations. The wafer saw cuts the individual dice from the wafer while leaving them on the adhesive tape. After which a die attach operation is performed. Referring now to prior art FIGS. 1 and 2, a typical die attach operation includes removing individual die 10 from the backing tape (adhesive film) 12 and attaching them to a packaging substrate (not shown), i.e., a leadframe, or a plastic or ceramic substrate. Plunge-up needles 14 are projected from a needle holder 16 and push the die from underneath through openings in an anvil 13 causing the die 10 and the adhesive tape 12 to disengage from one another thereby facilitating the transport of the die 10 to a collet (soft rubber vacuum pick-up) 12 on the pick-up head of the die attacher (not shown). The die attacher then aligns the die in its proper orientation and positions it on a die transfer pack or the packaging substrate.
Conventional plunge-up needle configurations and designs are adequate for GaAs die thicker than 4-mil. However, increased performance demands are imposing increased heat dissipation requirements, which in turn are forcing gallium arsenide chip manufacturers to consider designs wherein GaAs substrate thicknesses are on the order of 2-mil or less. At these thicknesses, die transfer tools and die attachers utilizing plunge-up needles to perform adhesive tape die separation operations can produce die fractures, such as the fracture 20 shown in FIG. 2, or even completely break the die. If detected, the fractures result in die scrap. If undetected, the fractures pose a problem with device reliability.
Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.